A piperazine derivative represented by the formula (1):
wherein n is an integer of 1 to 8; R
1
represents hydrogen or C
1-10
alkyl; A represents CH or nitrogen; Ar
1
represents phenyl or substituted phenyl; and Y represents a group represented by the formula Y
1
-Y
2
-Ar
2
or Y
3
-Y
4
(Ar
5
)-Ar
6
or a pharmaceutically acceptable salt of the derivative. The novel piperazine derivative has MC4 receptor antagonistic activity.
A piperazine derivative represented by the formula (1):
wherein n is an integer of 1 to 8; R1 represents hydrogen or C1-10 alkyl; A represents CH or nitrogen; Ar1 represents phenyl or substituted phenyl; and Y represents a group represented by the formula Y1-Y2-Ar2 or Y3-Y4(Ar5)-Ar6 or a pharmaceutically acceptable salt of the derivative. The novel piperazine derivative has MC4 receptor antagonistic activity.